From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-13.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7550BC433E0 for ; Mon, 4 Jan 2021 19:09:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 29EDC20770 for ; Mon, 4 Jan 2021 19:09:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726338AbhADTJQ (ORCPT ); Mon, 4 Jan 2021 14:09:16 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46852 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725921AbhADTJP (ORCPT ); Mon, 4 Jan 2021 14:09:15 -0500 Received: from ZenIV.linux.org.uk (zeniv.linux.org.uk [IPv6:2002:c35c:fd02::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 69992C061574; Mon, 4 Jan 2021 11:08:35 -0800 (PST) Received: from viro by ZenIV.linux.org.uk with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1kwVDU-006r5I-Ea; Mon, 04 Jan 2021 19:08:32 +0000 Date: Mon, 4 Jan 2021 19:08:32 +0000 From: Al Viro To: Eric Biggers Cc: linux-fsdevel@vger.kernel.org, Daeho Jeong , linux-kernel@vger.kernel.org Subject: Re: [PATCH v3] vfs: don't unnecessarily clone write access for writable fds Message-ID: <20210104190832.GL3579531@ZenIV.linux.org.uk> References: <20200922164418.119184-1-ebiggers@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: Al Viro Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Mon, Jan 04, 2021 at 10:55:15AM -0800, Eric Biggers wrote: > On Tue, Sep 22, 2020 at 09:44:18AM -0700, Eric Biggers wrote: > > From: Eric Biggers > > > > There's no need for mnt_want_write_file() to increment mnt_writers when > > the file is already open for writing, provided that > > mnt_drop_write_file() is changed to conditionally decrement it. > > > > We seem to have ended up in the current situation because > > mnt_want_write_file() used to be paired with mnt_drop_write(), due to > > mnt_drop_write_file() not having been added yet. So originally > > mnt_want_write_file() had to always increment mnt_writers. > > > > But later mnt_drop_write_file() was added, and all callers of > > mnt_want_write_file() were paired with it. This makes the compatibility > > between mnt_want_write_file() and mnt_drop_write() no longer necessary. > > > > Therefore, make __mnt_want_write_file() and __mnt_drop_write_file() skip > > incrementing mnt_writers on files already open for writing. This > > removes the only caller of mnt_clone_write(), so remove that too. > > > > Signed-off-by: Eric Biggers > > --- > > > > v3: added note to porting file. > > v2: keep the check for emergency r/o remounts. > > > > Documentation/filesystems/porting.rst | 7 ++++ > > fs/namespace.c | 53 ++++++++++----------------- > > include/linux/mount.h | 1 - > > 3 files changed, 27 insertions(+), 34 deletions(-) > > Ping. Applied.